In some applications, it is desirable for power converters to have a capability of supplying multi-level output voltages to electronic devices of different ratings. For example, the evolving Universal Serial Bus Power Delivery (USB PD) Standard prefers power supplies to provide supply voltages of, for example, 5V, 9V, 12V, 15V and/or 20V. Request for such diverse voltage levels may pose challenges to the design of power converters, especially with respect to the stability of power converters over a wide operating range. Commercially available components used in the control system of a power converter for one or more voltage levels (e.g., low voltages) may not be usable and/or available any more for other voltage levels (e.g., high voltages). For example, power supplies may typically employ one or more shunt regulators to implement closed loop control. A popular shunt regulator such as a 1.24V TLVH431 may fit a power supply of low voltage level(s) (e.g., 5V, 9V and/or 15V), but may not operate properly at high voltage level(s) (e.g., 20V) because of the shunt regulator's limited voltage rating. Conversely, a shunt regulator such as a 2.5V TL431 may fulfill the requirement of high voltage level(s) (e.g. 20V) because the TL431 regulator may withstand high voltage(s) up to 36V, but may not work reliably under low voltage(s) (e.g., 5V) because of instability issues. Therefore, what is needed is a design of control system to fulfill both performance and commercial requirements of multi-level power converters.